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[wxsig] Keying Kenwood HT and Current Consumption questions

Will Beals will at beals5.com
Mon May 1 03:04:05 UTC 2006


Thanks for the link.  Good news is the way I read the suggested schematic
onpage 104, I think you are set.  The PTT switch looks like it grounds the
microphone lead furthest from the tip.  You will need to get ground from the
speaker as shown, but that should not be a big deal.

I do AC-couple the audio for the microphone, but they sugget a larger
capacitor than I have on the T238.  I have a 0.1uf cap and they suggest a
10uf cap.  I hope that all makes sense.  If not, I can come up with a
suggested wiring diagram for you.

For power savings, I'd suggest simply plugging in the display for setup,
powering down, removing the display then powering up again.  The T238 should
come back up and run without the LCD.  Also should be no issue removing the
MAX232 as you point out.

Without the LCD, the regulator should be fine.  With the display I know I am
stressing that regulator with a source voltage greater than 12V.  I had a
wall wart sending out close to 14V and the regulator was going into thermal

Do let us know how the project progresses!


-----Original Message-----
From: wxsig-bounces at lists.tapr.org [mailto:wxsig-bounces at lists.tapr.org] On
Behalf Of Mark Patton
Sent: Sunday, April 30, 2006 5:04 PM
To: TAPR Weather Station SIG Mailing List
Subject: RE: [wxsig] Keying Kenwood HT and Current Consumption questions

Hi Will,

Below is the link to the manual to the HT that I'm thinking of using.  I
have an old ICOM dual-band HT that I'll be using for the "proto" - then will
move to the Kenwood once I get everything up and running properly.  
Thanks to the pointer on the power switch for the radio - I'll need that.  I
also found out that not all radios power up in the same configuration that
the power down in.  ie - I have a Yaseu VX-5 that comes up with the power
turned off if the battery is removed and replaced.


Page 104 has the wiring diagram.

To save power, I was thinking about installing a switch to turn off the
display light and/or to simply remove the display.  Wouldn't I need to have
the display attached to configure the date, sensors and call sign - then
remove the display?  I hate to do this with the power on so I was 
thinking of rigging in a power switch for the display.   I was also 
thinking of removing the Max232 since I don't need to be talking to a
computer.  The data sheet says it consumes 5ma that I could save. Any
thoughts on these ideas?

I will be running it from a 12V battery that may get up to 15V when
charging.  I will need to check the power dissipation of the regulator in an
enclosed box but if I remove the display and get the power down to 45-50ma,
I doubt that this will be much a problem.


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